Insertion aids for surgical instruments are used especially for minimal-invasive interventions in a patient's body to insert surgical instruments and/or endoscopes into a (possibly artificially created) body cavity. Depending on the place and purpose of use, the advantage of said insertion aids consists in the fact that either only small access orifices by appropriate tissue cuts are required so as to introduce appropriate instruments into the patient's body or that no external injuries whatsoever are caused for example in the case of a coloscopic or gastroscopic application. In this respect, for the insertion aids in question rigid as well as flexural tube or hose elements are provided which on the inside form at least one insertion duct of a predetermined diameter for pushing through the surgical instrument/endoscope.
A special form of such insertion aid is the trocar. This is an instrument with the aid of which an access to a body cavity such as the abdominal or chest cavity is provided in a sharp or obtuse manner and is kept open by a trocar sleeve (tube). The obturator initially introduced into the trocar sleeve is a pin or rod which is supported to be axially movable in the tube and the point of which closes the tube aperture. After introducing the obturator-trocar unit into the body cavity the surgeon then has the option after removing the obturator from the trocar to inspect the body cavity by an optical system (endoscope), for example, through the trocar or to operate in the body cavity through the trocar by surgical clipping and/or cutting instruments.
The tubes/trocars especially for inspection of body cavities (laparoscopy, thoracoscopy, arthroscopy etc.) may have a valve mechanism, a connection for insufflating (blowing in) a gas or a rinsing fluid or other supplementary equipment at their respective proximal extracorporeal end portion.
It is known from the state of the art to usually employ in the case of conventional laparoscopic interventions, for example, endoscopes having an (outer) diameter of 10 mm in connection with corresponding (rigid) trocars/trocar sleeves (tubes). As a rule, also the gas insufflation for generating and/or maintaining a pneumoperitoneum beneath the abdominal wall is carried out via said optical trocars as they are called. The tolerances for providing an annular gap between the optical system (outer diameter of endoscope) and the inner diameter of the trocar sleeve usually are dimensioned so that a sufficient gas passage is possible through the same in order to at least compensate for gas leakage from the pneumoperitoneum and thus to maintain the body cavity expanded (under gas pressure).
The miniaturization of the accesses, especially of the diameter of the surgical and optical instruments used including an endoscope in general in laparoscopy or endoscopy, for example, is more and more in progress, however, so that so called “single port” or single incision” interventions are more widely used as an option of use of these miniaturized instruments. Usually in the umbilical fossa a skin incision of only about 2 cm in length is made. By such incision for instance three 5 mm trocars (trocar sleeves/tubes) are then introduced via individual fascia incisions.
This novel technology is consequently facilitated by the use of a 5 mm optical system (endoscope) which initially basically constitutes no technical problem as such, as these optical systems in the meantime almost correspond to a 10 mm model as regards both the image and resolution quality and the light sensitivity. Moreover, the light intensity of lighting bodies (LED) of the latest generation is very high and hence the heat development is comparatively low so that modern optical systems and light-sensitive sensors (CMOS chips) are not excessively thermally impaired.
However, due to the afore-mentioned miniaturization new problems occur at other positions of the afore-described insertion aid-instrument-system which have not been known so far in this way, at least have not had any detrimental effects on the surgical working cycles. These include inter alia the problems emphasized in the following:
1. Insufficient Gas Insufflation
The maximum distal gas passage when using a 5 mm optical system (endoscope), for example, in combination with a corresponding 5 mm trocar (tube) turns out to be borderline low and considerably restricts the generation/maintenance of a pneumoperitoneum. If the pneumoperitoneum is to be built up completely anew, valuable time gets lost or it is not possible at all. The reason for this basically consists in the fact that the cross-section of the annular gap between the trocar sleeve and the instrument inserted in the same (optical system) is too small with an instrument diameter of 5 mm (with corresponding oversize on the trocar sleeve side) so as to attain a sufficient gas volume flow which at least compensates for the gas leakage flow. That is to say that in this case a limit for miniaturization for the insertion aid-instrument-system is not constituted by the technical/constructional possibilities of miniaturization concerning the optical system (endoscope) but by simple flow-mechanical conditions.
In this respect, a known design variant provides to form the trocar sleeve at the distal end portion thereof including a radial constriction (contraction) at the inside matching the obturator or instrument diameter so as to generate in this way sort of a throttle for the gas flow and at the same time to reach an improved distal guide of the instrument inserted in the trocar sleeve (tube). Ahead of the radial constriction at the inside (in the proximal direction) the lumen of the feed passage inside the tube is radially expanded by several tenths of millimeters, however, so that an annular gap is formed between an inserted instrument and the trocar sleeve.
So that sufficient gas can exhaust via the trocar into the body cavity despite the arrangement of the afore-described radial constriction or contraction at the distal end of the trocar sleeve, a number of lateral exit bores are introduced in the trocar sleeve partially closely (proximally) ahead of the constriction/contraction from which exit bores gas may escape laterally (in the radial direction) into the pneumoperitoneum. Since, however, the gas must flow through the still narrow annular gap proximally relative to the radial exit orifices, the exiting maximum gas volume flow remains to be basically limited.
2. Relatively Heavy Stains of the Optical System
With a 2 cm incision according to the foregoing description usually smaller blood vessels are injured which result in a minor seeping haemorrhage at least temporarily after introducing the trocars. Gradually one or more drops of blood and tissue fluid accumulate at the distal point (distal leading edge) of the trocar sleeve. If the optical system (endoscope) protruding at the distal trocar sleeve end is now pulled out of or retracted from the trocar sleeve for cleaning the lens, for example, which is necessary from time to time in order to remove precipitation obstructing the view (the latter is formed after a particular OP period by the use of HF or ultrasonic application, for instance), the blood/tissue fluid drop adhering to the leading edge is also sucked into the trocar sleeve and stains/covers the latter at the inside of its duct wall. If now the cleaned optical system (endoscope) is now re-introduced into the trocar sleeve (having a small annular gap dimension), thus the fluid adhering at the inside is stripped off at least in parts and thus immediately stains at least the border of the lens again.
Although in the 10 mm optical systems (endoscopes) common so far this problem basically arises as well, but it is definitely weakened for the following reasons, however:                When the optical system (endoscope) is pushed forward again, due to the larger annular gap width between the optical system (endoscope) and the trocar sleeve more fluid is retained in the annular gap and thus does not at all get onto the optical system (or the lens).        Due to the larger optical system (lens) proportionally a smaller (border-side) area of the optical system or lens is stained, wherein this staining has only little influence on the performance of the optical system.        